1. Field of the Invention
The present invention relates to an image pickup device capable of operating in a mode selected from a plurality of exposure control modes including a manual exposure control mode, and to a computer-readable storage medium on which a program for controlling the image pickup device is stored.
2. Related Background Art
Recent automated cameras have a system for automatically determining the amount of exposure by using a central processing unit (CPU) incorporated in the camera. Such a system enables easier photographing in each of an aperture value priority mode, a shutter speed priority mode, a mode of photographing based on a predetermined program diagram (program), etc.
Some electronic cameras using an image pickup element such as a charge-coupled device (CCD) are designed so that the image pickup element is also used as a photometric sensor for the purpose of reducing the manufacturing cost. In such cameras, since the image pickup element is used as a photometric sensor, signals representing data, for example, on image brightness, colors, and sharpness are extracted from an image imaged on the image pickup element, and control operations, such as automatic exposure, white balancing, automatic focusing and strobe light control are performed on the basis of the signals.
An image imaged on the image pickup element is output through an image output device, such as an electronic view finder using a liquid crystal display (LCD) or the like, or a video output device. When an operator checks the image imaged on the image pickup element, for example, by outputting the image through the image output device, exposure control for maintaining the main object at a certain brightness level is required.
On the other hand, the operator can make the camera perform automatic exposure control after selecting at least one of desirable exposure control values: an aperture value AV, a shutter speed TV, and a sensitivity SV and selecting one of exposure control modes, such as an aperture value priority mode and a shutter speed priority mode. The operator can also make the camera perform exposure control with values all set by the user in a manual mode or the like.
The operator can also make the camera perform automatic exposure control in a photographing mode in which a shutter speed or an aperture selection effect can be obtained while no exposure control value is designated, e.g., a high-speed shutter mode using a program diagram such that a higher shutter speed is set, or a landscape mode using a program diagram such that a smaller aperture value is set.
The operator can also make the camera perform light control during photographing using a strobe in such a manner that photometry is performed when a strobe does not emit light to an object and when the strobe emits light as a pre-emission to the object, and the reflectivity of the object is computed from the difference between the two photometry results to determine the quantity of light to be emitted at the time of actual photographing. It is, of course, possible for the operator to perform a manual control operation for determining the quantity of light to be emitted by the strobe.
However, in taking a picture of an object under some conditions, including a selected exposure control value, there is a possibility of failure to display an image on an image output device suitably enough to ensure sufficient facility with which the image is framed.
In particular, a photographing operation that presupposes the use of strobe light may require an underexposure setting, depending on the quantity of strobe light. In such a case, if exposure control is performed without regard to the underexposure condition, the image is displayed in a dimmed condition on the image output device and cannot be easily framed.
For example, in a case where there is a difference between the aperture value AV, the shutter speed TV and the sensitivity SV set with respect to an object in automatic-exposure photographing and the aperture value AV, the shutter speed TV and the sensitivity SV set with respect to the object in photographing with strobe light, a difference in brightness of the images output to image output device may occur between these two photographing modes. In contrast to automatic exposure, a certain amount of underexposure is ordinarily set in photographing with strobe light by considering the superimposition of the quantity of strobe light on an object. Therefore, when the aperture value AV, the shutter speed TV, etc., are set with respect to an object in photographing with strobe light, the amount of underexposure may be considerably large, depending on conditions relating to the object.